Predictive Factors of Nonmalignant Pathological Diagnosis and Final Diagnosis of Ultrasound-Guided Cutting Biopsy for Peripheral Pulmonary Diseases

This study aimed to explore the predictive factors of nonmalignant pathological diagnosis and final diagnosis of ultrasound-guided cutting biopsy for peripheral pulmonary diseases. A total of 470 patients with peripheral lung disease diagnosed as nonmalignant by ultrasound-guided cutting biopsy in the First Affiliated Hospital of Guangxi Medical University from January 2017 to May 2020 were included. Ultrasound biopsy was performed to determine the correctness of pathological diagnosis. Independent risk factors of malignant tumor were predicted by multivariate logistic regression analysis. Pathological biopsy results showed that 162 (34.47%) of the 470 biopsy data were specifically benign, and 308 (65.53%; malignant lesions: 25.3%, benign lesions: 74.7%) were nondiagnostic findings. The final diagnoses were benign in 387 cases and malignant in 83 cases. In the nondiagnostic biopsy malignant risk prediction analysis, lesion size (OR = 1.025, P = 0.005), partial solid lesions (OR = 2.321, P = 0.035), insufficiency (OR = 6.837, P < 0.001), and presence of typical cells (OR = 34.421, P = 0.001) are the final important independent risk factors for malignant tumors. In addition, 30.1% (25/83) of patients with nonmalignant lesions who were finally diagnosed with malignant tumors underwent repeated biopsy, and 92.0% (23/25) were diagnosed during the second repeated biopsy. 59.0% (49/83) received additional invasive examination. Nondiagnostic biopsy predictors of malignant risk include lesion size, partial solid lesions, insufficiency, and presence of atypical cells. When a nonmalignant result is obtained for the first time, the size of the lesion, whether the lesion is subsolid, and the type of pathology obtained should be reviewed.


Introduction
More than 2 million new cases of lung cancer and about 1.79 million patients who died from lung cancer were reported in 2020, which remained the leading cause of death among patients with cancer [1]. An increasing number of patients have been found to meet the screening criteria for lung cancer using CT scans. Terefore, the incidence and detection rate of peripheral pulmonary diseases have gradually increased in recent years [2,3]. Percutaneous lung biopsy guided by imaging technology is a useful and well-known method. Peripheral pulmonary diseases are located in the segment and below the bronchus and close to the chest wall, which provides the feasibility of ultrasound. Ultrasound can provide precise positioning and visual detection. It is a nonradiation, fast, economical, and efective guidance method. Ultrasound-guided puncture biopsy of peripheral pulmonary diseases has an acceptable diagnostic rate, and the complication rate is lower than that of CT-guided biopsy [4][5][6][7]. Terefore, ultrasound should be recommended because peripheral pulmonary diseases can be observed through the use of ultrasound. Tissue biopsy is the gold standard for diagnosing benign and malignant lung nodules or tumors [8]. Te diagnosis of lung malignant tumors, benign-specifc diagnosis, and the presence of positive biopsy cultures by percutaneous lung biopsy are considered as true refections of the disease [9][10][11]. However, when inconclusive diagnoses such as nondiagnostic results or insufcient specimens are obtained, the reliability of the biopsy using this technology is low, which puts clinicians into a dilemma [12,13]. Based on a multicenter study in recent years, the negative predictive value of CT-guided lung biopsy for the diagnosis of malignant diseases is only 51% [14]. Terefore, accurately diagnosing the pathological characteristics of these nodules or masses and distinguishing malignant and benign lesions are necessary for treatment planning.
Although some relevant studies have been published, the number of studies that analyze the initial pathological report of percutaneous lung biopsy that yielded a nonmalignant diagnosis and the number of cases included in peripheral pulmonary diseases are limited [13][14][15], and they primarily focus on CT as an image-guided method or fne needle aspiration method [15][16][17]. In the vast majority of research reports, no research has focused on the analysis of large sample sizes of nonmalignant lesions in the frst biopsy of nonmalignant lesions under the guidance of ultrasound. Terefore, this study aims to analyze the fnal diagnosis of nonmalignant lesions in the initial biopsy and the predictive factors of benign and malignant nondiagnostic lesions based on a larger sample of data.

Study Objects.
A total of 957 percutaneous lung biopsy data of patients diagnosed with peripheral lung disease and accompanied by ultrasound-guided percutaneous lung biopsy in the First Afliated Hospital of Guangxi Medical University from January 2017 to May 2020 were selected, and 487 biopsy data with malignant diagnosis were excluded. Te inclusion criteria were as follows: (1) peripulmonary space occupying lesions confrmed by CT; (2) have indications for lung biopsy and the family members sign the informed consent of biopsy; and (3) ultrasonography can clearly show the focus. Te exclusion criteria were as follows: (1) patients with contraindications of lung biopsy (coagulation dysfunction; severe cardiopulmonary insufciency such as severe pulmonary hypertension; anatomic or functional isolation of the lung; evident infectious lesions along the puncture path, bullosa, chronic obstructive pulmonary disease, emphysema, and pulmonary fbrosis; mechanical ventilation (ventilator); radiographic consideration of pneumoechinococcosis); (2) those who received ultrasound-guided percutaneous biopsy without pathological examination; and (3) malignant disease diagnosed by puncture biopsy. Te general information of the patient was recorded. Tis retrospective single-center study was approved by the ethics committee of the First Afliated Hospital of Guangxi Medical University (approval number: 2021[KY-E-199]). Given the retrospective nature of this study, the requirement to sign informed consent was exempted.

Puncture and Biopsy.
Bard biopsy needle (16 G and 18 G types) was soaked in 75% ethanol solution and covered with a disposable sterile plastic flm for 10 min to ensure sterility. GE logiq E9 or Siemens Acuson S2000 conventional ultrasonic diagnostic instrument was adopted, and the probe frequency was 2.5-4.0 MHz or 3.55.5 mhz. Based on the specifc location and size of the lesion, blood supply, the adjacent relationship of the lesion with the surrounding tissues displayed on the ultrasound image, patient's body position, and the best puncture path were determined. Routine disinfection, lying of surgical towel, and administration of local anesthesia with 1-2 mL of 2% lidocaine were described. Avoiding the heart and large blood vessels, the needle tip of the Bard adjustable biopsy gun was inserted into the target lesion in accordance with the predesigned puncture path. When the needle path was clearly displayed, the patient was required to hold his breath, trigger the shooting, and withdraw the needle. Afterward, the sample was stored in 4% formaldehyde solution for pathological examination. Te occurrence of complications such as hemoptysis, pneumothorax, and pleural reaction was observed.
If the patient performs two or three biopsies on the same target lesion, these repeated biopsies are counted as independent events.

Final Diagnosis.
Te fnal diagnosis was performed in combination with patient's medical history and subsequent treatment examination results [16,19,20]. Te fnal diagnostic criteria were as follows: (1) if all diagnostic results are consistent, the clear diagnosis is confrmed; (2) the results of surgical pathology report and biopsy report are contradictory, and the surgical case report shall prevail; (3) when the pathological results include malignancy, the malignant diagnosis is used; and (4) the patients were followed up for at least half a year. In the absence of chemotherapy, radiotherapy, and anticancer drug treatment, the CT results showed that the diameter of the lesions decreased or remained unchanged, and they were diagnosed as benign lesions. In the presence of evident metastasis or progression of malignancy during follow-up CT, the diagnosis is considered as malignant.

Statistical
Analysis. Using SPSS 25.0 for statistical analysis of data, continuous variables were expressed as mean ± standard deviation (SD), and two independent sample t-test was used for comparison between the two groups. Categorical variables were expressed by frequency (percentage), and the chi-squared test was used for statistical analysis. Multivariate logistic regression analysis was used to test the infuencing factors of malignant lesions. P < 0.05 was considered statistically signifcant. Figure 1 illustrates the fow chart and diagnostic results of patient screening for initial PTNBs. Also, the baseline characteristics are shown in Table 1 Among the 470 nonmalignant diagnostic biopsies, the distribution of initial pathological diagnosis and fnal diagnosis is shown in Table 2. Among the 470 patients, 34.5% (162/470) had specifc benign diagnostic results; 54.7% (257/470) had a nonspecifc benign diagnostic result, and 10.9% (51/470) had inconclusive results. Among the 162 cases of specifc benign diagnostic biopsies, 3.1% (5/162) were diagnosed as malignant, and 96.9% (157/162) were diagnosed as benign lesions. In addition, among the 257 cases of nonspecifc benign diagnostic biopsies, 17.5% (45/ 257) of the fnal diagnosis was malignant, and 82.5% (212/ 257) was fnally diagnosed as benign lesions. Among the 51 cases of inconclusive lesion diagnosis, 90.9% (10/11) of 11 cases of atypical cell diagnosis were fnally diagnosed as malignant, and 9.1% (1/11) were fnally diagnosed as benign lesions. Out of the 40 cases with insufcient tissue diagnosis, 57.5% (23/40) was fnally diagnosed as malignant, and 42.5% (17/40) was fnally diagnosed as benign. Among the 470 included cases of nonmalignant diagnosis, the fnal diagnosis of benign and malignant lesions accounted for 82.3% (387/470) and 17.7% (83/470), respectively ( Table 2).

Multivariate Logistic Regression Analysis of Nondiagnostic
Biopsy. Among the 308 nondiagnostic biopsies, the fnal diagnosis of benign and malignant was 74.7% (230/308) and 25.3% (78/308), respectively. Te demographic data and lesion characteristics were compared between the benign group and the malignant group of 308 nondiagnostic biopsies (Table 3). Malignancy mostly occurred in larger masses (>15 mm, P � 0.001), the right lung (P < 0.001), and the middle or lower lobe of the lung (P < 0.001), and the prone position was more adopted during puncture (P � 0.01). In addition, atypical cells and insufcient diagnostic tissue had a higher risk of fnal malignancy than nonspecifc infammatory lesions (P � 0.001). No statistically signifcant diferences in gender, age, nature of the lesion, cutting needle type, puncture angle, and puncture times were observed.

Final Malignant Diagnosis and Initial Diagnosis of 83 Nonmalignant Lesion Cases.
Te results of 83 cases of initial diagnosis of nonmalignant lesions and fnal diagnosis of malignancy were further evaluated, out of which 30.1% (25/ 83) received repeated biopsy and 92.0% (23/25) received second repeated biopsy to confrm the diagnosis. In addition, 8% (2/25) underwent a third puncture biopsy, which was fnally diagnosed as malignant. Additional invasive examinations were received by 59.0% (49/83), and 10.8% (9/ 83) confrmed the diagnosis of malignancy through clinical follow-up ( Figure 2 and Table 5).

Discussion
In this study, the predictive factors of nondiagnostic pathological results and potential malignant tumors, the size of the lesion, the type of the lesion, the presence of atypical cells, and the insufciency of tissue were evaluated through analysis of baseline data, image characteristics, operationrelated techniques, and pathological types. Each pathological type of nondiagnostic lesions has a diferent rate of malignancy. Te malignancy rate of atypical cells is as high as 90.0% (10/11), followed by 57.5% (23/40) of insufcient tissue, and that of nonspecifc benign lesions is 17.5% (45/ 257). Trough the follow-up of the nonmalignant results of the initial puncture biopsy, 30.1% (25/83) had repeated biopsies, 59.0% (49/83) received additional invasive examinations, and 10.8% (9/83) confrmed malignancy through clinical follow-up diagnosis.
In a retrospective analysis of 470 cases of ultrasoundguided cutting biopsy of peripheral pulmonary diseases for the frst pathological diagnosis of nonmalignant lesions during 3.5 years, the fnal diagnosis of benign and malignant lesions accounted for 82.3% (387/470) and 17.7% (83/470), respectively. In some of the published studies on lung lesion biopsy guided by imaging technology, the incidence of initial nondiagnostic biopsy of malignancy accounted for 16.4%-50% [10,14,17,21]. Terefore, our research results are consistent with the literature reports of previous studies. In a study of transthoracic CT-guided coaxial puncture aspiration biopsy, Rui et al. fnally determined 141 malignant cases (16.4%) and 720 benign cases (83.6%) [17]. Similar to our results, the 141 patients (141/861, 16.4%) who were fnally diagnosed with malignancy in the study of Rui et al.

Canadian Respiratory Journal
were all from the "unspecifed infection," "infammatory disease," or "indeterministic" group [17]. Among the 83 patients who were fnally diagnosed with malignancy in this study, fve had specifc benign lesions such as tuberculosis and infammatory pseudotumors at the frst diagnosis. In a study of the predictive factors and fnal diagnosis of nondiagnostic results of CT-guided percutaneous lung biopsy, Tongbai et al. [15] found that 36% of nondiagnostic cases were ultimately diagnosed with malignancy. In this study, only 17.7% of nondiagnostic cases had a malignant diagnosis, which was signifcantly lower than that reported by Tongbai et al. Tis diference may be due to the broader defnition of nondiagnostic biopsy in this study. Tongbai et al. attributed pathological fndings such as organized pneumonia and granulomatous infammation to specifc benign diagnosis. In our study, organized pneumonia, granulomatous infammation, and abscesses, which have inconclusive specifcity, are classifed as nonspecifc benign lesions.
Among the 470 patients included in this study, the proportion of specifc benign was 34.5% (162/470), which was higher than that (21%) reported by Quint et al. in a study on the value of CT-guided coaxial puncture biopsy with negative results. Tis study is similar to Quint et al.'s study [22] in determining the diagnostic criteria for specifc benign lesions probably because the specifc benign ratio of tuberculosis in the pathological diagnosis of puncture biopsy in this study is as high as 63.0% (102/162). Based on literature, our country is one of the countries with the heaviest tuberculosis burden worldwide. Tuberculosis has a high incidence rate in our country [23], whereas Quint et al. conducted research in the United States, where the number of patients with tuberculosis is limited. However, compared with the specifc benign diagnostic rate of 77% (17/22) reported by Satoh et al. [24], the reason why the diagnostic rate of specifc benign lesions in our study is lower than that in this study remains unclear probably because of the diferences in countries, ethnic groups, or manifestations of the disease.
Among the 308 nondiagnostic biopsies in this study, the percentage of nonspecifc benign lesions, atypical cells, and insufcient pathological report diagnosis was about 83.4% (257/308), 3.6% (11/308), and 13% (40/308  insufcient specimens were 50.5% (52/103), 15.5% (16/103), and 40% (35/103), respectively. Te proportion of nonspecifc infammation in our study is signifcantly high, whereas the proportion of atypical cells and pathologically reported insufcient tissue is low probably because a relatively large cutting needle of 16 G or 18 G was used in this study, which improves the output and accuracy of the diagnosis. In a multicenter study on nondiagnostic pathology, the risk assessment of malignant tumors by percutaneous lung biopsy conducted by Lee et al. [16] found that the percentage of nonspecifc infammation, atypical cells, and insufcient specimens was 61.5%, 21.5%, and 17.0%, respectively. Our nonspecifc infammation ratio is high; the insufcient tissue is low; and the presence of typical cells is signifcantly low. Tis diference in results might be due to the fact that the study conducted by Lee et al. [16] was guided by CT, radiation, ultrasound, and other imaging techniques.
In the selection of puncture needle type, fne needle aspiration and cutting needle cutting were used alone or in combination. However, this study is purely ultrasoundguided puncture biopsy of peripheral pulmonary diseases, and it uses a large 16 G or 18 G cutting needle, which is sufcient for obtaining tissue samples. Most of the tissue specimens obtained can be examined by immunohistochemistry, thereby improving the diagnosis. With regard to the proportion of fnal malignancy in this study, nonspecifc benign lesions, insufcient tissue, and atypical cells accounted for 17.5% (45/257), 57.5% (23/40), and 90.9% (10/ 11), respectively. Tis fnding is consistent with the results of previous studies, with 21.3%-37.2% and 46.6%-50% for nonspecifc benign tumors and insufcient specimens, respectively, in the fnal diagnosis of malignancy under the guidance of imaging technology [16,17,22]. We reported that the proportion of the fnal malignant diagnosis of atypical cells is higher than that reported by other studies (62.5% or 64.3%, 10/14) [13,15], which is similar to the results of Lee et al. [16] in a large multicenter sample study. In this study, by observing the risk of fnal malignancy of pathological types in nonmalignant diagnosis, compared with nonspecifc benign lesions and insufcient specimen pathological report diagnosis, atypical cells likely have malignancy. In addition, when the puncture biopsy shows nonspecifc benign lesions or insufcient tissue, the possibility of malignancy cannot be completely ruled out.

Canadian Respiratory Journal
In the univariate analysis of this study, lesion location 1 (right lung, left lung), location 2 (upper lobe, middle or lower lobe), and patient's position (supine, lateral, and prone) are considered as predictors. Malignancy is common in the right lung as well as middle and lower lobe, and the prone position is commonly used during puncture. After multivariate analysis, P values of the abovementioned variables are all >0.05. In multivariate analysis, the predictive  factors of the nondiagnostic outcome of malignancy include the size of the lesion, the type of the lesion, the presence of atypical cells, and the insufcient tissue for diagnosis. Te variable related to malignancy in this study is the size of the lesion. Tis view is consistent with the fndings of Rui et al. [17]. Terefore, in nondiagnostic lesions, the larger the lesion, the higher the risk of malignancy. Some literature reports that the larger the lesion, the higher the incidence of false negatives [25][26][27]. Gelbman et al. [9] also pointed out that larger lesions are more prone to false negatives in their radiological and clinical characteristic studies on the false negative results of CT-guided lung nodule biopsy. In this study, after multivariate analysis, subsolid nodules are more likely to be malignant than solid nodules because of various factors, which is consistent with the results of previous studies [28,29]. However, Yun et al. [30] compared 354 patients with lung biopsy guided by CT and analyzed the diagnostic rate, biopsy-related factors, and complications of solid and subsolid lesions, and the results showed that nondiagnostic biopsy had no statistical diference between solid and subsolid lesions. Lee et al. [16] retrospectively analyzed 2590 lung biopsy cases and classifed them into three categories: nonspecifc benign lesions, atypical cells, and insufcient specimens. Te results show that atypical cells that are suspected of being malignant are more likely to be diagnosed more malignant than atypical cells that are inconclusive. In nonspecifc benign lesions, granulomatous infammation, abscesses, and organized pneumonia are independent factors for eliminating malignancy. In a multivariate analysis of 122 cases of benign and malignant nondiagnostic lesions, Tongbai et al. [15] proposed that nondiagnostic biopsies with a history of malignancy or pathologically atypical cells are more likely to be malignant. In this study, the presence of atypical cells is an important independent risk factor for the fnal diagnosis of nondiagnostic lesions as malignancy, which is consistent with the abovementioned literature reports. During tissue sampling, due to various reasons such as lesion size and location, tissue sampling was insufcient and sample size was small, so it was possible that the lesion site could not be obtained, resulting in false negative results. When there is a benign diagnosis due to insufcient sample size, the possibility of malignancy cannot be ruled out, and we should conduct verifcation again if conditions permit.   In our study, 30% (25/83) of 83 patients who were initially diagnosed with nonmalignant lesions and fnally diagnosed as malignancy underwent repeated biopsy, 59.0% (49/83) underwent additional invasive examination, 10.8% (9/83) confrmed the diagnosis of malignancy through clinical follow-up radiology. 25 cases underwent the second repeat biopsy, of which 23 (92%, 23/25) fnally confrmed the diagnosis, and 2 cases confrmed the malignant diagnosis after the third repeat biopsy. It can be seen from this study that a higher diagnostic rate can be obtained through repeated biopsy. Previous research reports have also confrmed this view [14][15][16]25]. Montaudon et al. [26] found that the same target had a negative predictive value of 100% in the second biopsy. In a study of 950 transthoracic CTguided biopsy patients with nonmalignant lesions found for the frst time, Rui et al. [17] pointed out that 47.6% of patients underwent additional invasive tests to confrm the fnal diagnosis. In this study, 59.0% (49/83) received additional invasive tests to confrm the diagnosis of malignancy. Terefore, for the biopsy results of the nondiagnostic lesions, additional diagnostic tests should be performed when necessary. Savage et al. [21] also put forward this point of view.
Tis study has certain limitations: frst, it is a retrospective analysis study, some data lacking is excluded, and there is a certain bias. Second, this study failed to analyze the patient's malignant tumor history, smoking history, family history of lung cancer, and complications of puncture biopsy. Finally, since most puncture biopsies are used to clearly diagnose lung lesions that are suspected of being malignant, in further research, the accuracy and diagnosis failure of malignant tumors will be studied and analyzed.

Conclusion
Te diagnostic rate of ultrasound-guided cutting biopsy for peripheral pulmonary diseases is acceptable, which has certain application value in clinic. Te predictors of benign and malignant nondiagnostic biopsy include the presence of atypical cells, the insufciency of diagnostic tissues, and the type of the lesion and the size of the lesion. Terefore, when a nonmalignant result is obtained, the lesion should be reviewed to determine whether there are any factors, including the size of the lesion, the type of the lesion, and the type of pathology obtained. If necessary, a repeated biopsy or additional invasive examination should be performed. Such additional evaluation and careful monitoring can help doctors further identify nonmalignant peripheral pulmonary diseases to confrm the fnal diagnosis.

Data Availability
Te data used to support the fndings of this study are available from the corresponding author upon request.

Conflicts of Interest
Te authors declare that there are no conficts of interest regarding the publication of this paper.